Gas hammer speed control



Sept. 19, 1950 c, s, w D 2,522,550

GAS HAMMER SPEED CONTROL Filed Dec. 19, 1946 INVHVTOR.

Cm Mm/mr Patented Sept. 19, 1950 UNITED STATES FATENT OFFICE 4 Claims.

This invention relates generall to the control of the operation of aninternal combustion percussion tool and more particularly to a manualcontrol of the speed of th timing piston of an internal combustionpercussion tool to regulate the frequency of reciprocation of theworking piston and prevent the timing piston from racing away from theoperation of the working piston.

In internal combustion percussion tools employing a captive timingpiston and a slave working piston, there is very little load on thecrankshaft of the timing piston as its only function is to control theoperation of the tool to generate and ignite the spark and valve theports for the admission of fuel to the combustion chamber where theenergy is transferred to the working piston for the purpose of producinguseful work. Thus the speed of operation of the working piston may beregulated by the control of the speed of the timing piston. The extremelight load on the timing piston permits it to frequently speed up andthereby get out of step with the operation of the working piston causingthe latter to cease operation and prevent it from delivering usefulwork. When the working piston gets out of step with the timing piston itfails to operate on successive explosions making the tool useless as apercussive tool.

Different types of speed devices have been employed for controlling,checking or otherwise retarding the excessive speed of the captivepiston in percussive tools of this character. Some methods of producingthis result is by the use of a spark cutout or throttle control. Howeversuch modes necessitate the operation of the captive piston until itsfriction causes it to redues in speed sufficiently to reconnect thespark or resupply the fuel and cause the tool to again function as apercussive tool. This mode of control is undesirable because it takestoo long for the timing piston to reduce its speed.

Another mode of controlling the speed of the captive piston is theprovision of a centrifugal governor arranged to actuate an air vane inthe carburetor to check the input flow or" fuel to the engine. Thisreduces the speed of the captive piston by lowering the supply of fuel.However it also reduces the power input to the working piston therebyoperating the tool inefficiently making an undesirable speed control.

Another mode of controlling the speed of the captive piston is by theuse of a speed governor arranged to apply a centrifugal brake on thecrankshaft of the captive piston. This mode requires expenditure ofenergy in the form of friction, and the brake mechanism is not onlysubjected to wear but is very sensitive and requires frequent adjustmentmaking it disadvantageous for this use.

Another mode of controlling the speed of the captive engine is by theuse of means correlated with the speed of the captive piston arranged tocontrol the flow of exhaust gases from the internal combustion chamberto thereby regulate the speed of the operation of the tool. This mode ofcontrol produces a contaminated mixture of fuel in the combustionchamber causing a reduction of power in the tool making it undesirableas a control.

Each individual internal combustion tool has its own particular speedcharacteristics due to differences in friction, valve locations withinmanufacturing tolerances, humidity and variations in fuel for the mostefiicient operation in obtaining the greatest power output. Suchautomatic controls functioning independently of control by th operatorwill not produce the most efiicient operation of the tool.

The principal object of this invention is the provision of a deviceproviding a manual control of the speed of the captive piston which issimplified in design and which does not have the disadvantages of theautomatic controls.

Another object is the provision of a manual speed control for aninternal combustion percussion tool which permits the operator to exactfull load operation from the tool as required at various working speeds.

Another object is the provision of a manual speed control for aninternal combustion percussion tool that permits operation of the toolwithout decreasing the number of power strokes or the energy deliveredto the percussion piston at any desired working speed.

Another object is the provision of a simple and economical manual speedcontrol for an internal combustion percussion tool which does Fig. 1 isa sectional view of an internal combustion percussion tool having amanual fingertip speed control applied thereto.

Fig. 2 is a sectional view of the manual combustion percussion tooltaken on the line 22 of Fig. 1.

The present invention provides a manually operated control of the speedof the timing piston of an internal combustion percussion hand tool.This hand tool is operated from the vertical to the horizontal positionand may be employed as a hammer, a drill, a ballast tamper, a concretebuster or for performing similar useful work. This hand tool iscompletely self-contained as it does not require the use of asupplementary apparatus in its operation.

Referring to the drawing, the internal combustive percussive toolcomprises a cylinder at having a timing piston II and the percussionworking piston !2 arranged to operate therein. lhe timing piston I I isoperatively connected with the balanced crankshaft i3 by means of theconnecting rod M. One end of the crankshaft i3 is provided with acovered starting pulley I5 and the other end carries a flywheel IEhaving fan blades for the purpose of supplying a stream of air to coolthe internal combustion tool. A crankcase head I! is attached to theupper end of the cylinder H] and is adapted to carry the alignedcrankshaft bearings and other stationary parts of the gas hammer, suchas the bracket l8 on which is mounted a handle [9 with the fuel throttlelever together with the housing 2| which encloses the flywheel Hi, thefuel tank 8, and the carburetor 9. All of these parts are secured to thecrankcase l1 and the cylinder H) and provides a relatively small andcompact and unitary tool.

A tool holding member 22 is bolted to the lower end of the cylinder I!)by means of the four tie bolts 23 which are fastened at their upper endsthrough the bracket l8 and which extend the full length of the crankcasehead I1 and cylinder [0. The tool holding member 22 is bored to receivethe working piston guide 24 which extends into and fits the bore of thedifferential chamber 25 of the cylinder H3, and is provided with aflange clamped between the end of the cylinder and tool holding memberas shown in Fig. 1.

The percussive working piston l2 has a depending stem 26 with a strikingportion extending through the guide 24 and is arranged to strike the topof the tool 2'! which is slidably supported within predetermined limitsin the bore of the tool holding member 22 and is re tained by the springlatching member 28.

The percussive working piston I2 is a differential piston and thecombustion or smaller end of this piston controls the port leading fromthe combustion chamber 30 through the valve control passageway 3! to thechamber 25 at the other end of the working piston for supplying productsof combustion under pressure which are effective against the larger endof the working piston !2 for returning the same. The valve 32 in thepassageway 31 is actuated by means of the reach rod 29 pivotallyconnected to the handle throttle lever 20 mounted on the handle I9,which throttle also controls the operation of the carburetor insupplying fuel to the engine.

The flywheel i6 is hollow and encloses a magneto and braker points forthe purpose of'supplying the ignition of the internal combustion tool.These points are not shown but the braker arm cam is shown on thecrankshaft at 33. The fan blades 34 are attached to the outer face ofthe flywheel I5 adjacent its perimeter and they form a vortex which isdisposed adjacent the screened opening 35 in the housing 2! thatsurrounds the fan and tapers downwardly to around the lower end of thecylinder ll] partially covering the same, causing the air streamgenerated by the fan to flow transversely around the cylinder H3 betweenthe cooling fins.

A brake pulley 36 is an integral part of the starting pulley l5 and liesbetween this pulley and the crank head housing IT. The brake pulley 35consists of a rim section 53 connected by spokes 54 to the hub 55 of thestarting pulley i5. As shown in Fig. 2 the rim 53 is in section and theupper part of the pulley is shown in elevation as indicated at 56. Thispulley is slightly larger in diameter than the starting pulley and isprovided with a perimetral surface functioning as a friction brakesurface. The brake band lining 31 comprises the strap member 38 securedat one end to the bolt 40 which is adjustably fastened to the bracket itby the nuts ii and as. The lining 31 is secured to the band 3.8 by theusual rivet members 43. The other end of the band 38 is provided with acylindrical socket member M which is slotted in the center as indicatedat 5 for the purpose of receiving the stem portionfi of the manualcontrol member ll. The lower end of the stem 456 is secured to the crossmember 48 pivotally carried in the cylindrical socket member M. Theupper end of the stem iii projects into an opening in the underside ofthe handle l9 and is provided with an offset bracket member 50, theouter end 5| of which is turned outwardly and arranged to engage on thebottom of the tubular handle member l 9 thus limiting the downwardmovement of the control member d1. The offset portion of the bracketmember 59 is provided with a finger engaging 'surface 52 directly belowthe throttle lever 20.

The brake band 38 is adjusted by the nuts 4! and 42 to provide clearancefor the pulley 36 when the stop 5! is at its lowermost position as shownin Fig. 2'. Any slight upward pressure on the finger engaging surface 52causes the brake band to be contracted on the brake pulley 36 effectinga friction brake on the surface of the brake pulley. A slightapplication of this brake band is immediately effective to reduce thespeed of the shaft i 3 thereby reducing the speed of the captive timingpiston H. The application of the brake band on the pulley is such thatit tends to draw the brake band into frictional engagement when brakepressure is applied thereto.

During operation of the internal combustion percussion tool the operatorin supporting the tool by the tubular handle if! can feel when a changein load on the tool causes the captive timing piston to increase itsspeed, and immediately check the speed of the timing piston and thusmaintain the same output of the working piston regardless of the changein load on the tool. In fact the operator can anticipate changes in loadby watching the work of the tool, and with a slight application of thebrake reduce the speed of the timing piston before it has had a changeto race away from the operation of the working piston.

By manually controlling the operation of the internal combustionpercussive tool in this manner maximum output may be obtained from thetool at all times irrespective of the change in load. This improvedoperation is not obtainable by any of the other modes of controlling thespeed of the captive timing piston and represents the most importantfeature of this invention. By the use of this manual brake control, anoperator is enabled to obtain maximum work per unit of time which isimpossible by the use of any automatic control. This also represents avery important object of this invention.

An important object of this invention is the provision of a speedcontrol for an internal combustion percussion tool which permits theoperator to instantly regulate the striking power of the blow of thetool between zero and a maximum power output and also permits him tostop the tool instantly and independently of the throttle. This controlof the power output of the tool cannot be obtained to the same extent byother modes of controlling the speed of the hammer. It is exceedinglyimportant to provide instant power control over a percussion tool ofthis character as it increases its utility and permits the operator towork with greater efficiency.

The operator may constantly apply a predetermined load on the timingpiston through the brake to operate the percussion working piston at anydesired working speed and exact maximum power output on each powerstroke of the working piston. Thus the operator has complete controlover the independently operating working piston by controlling the speedof the timing piston and thereby controlling the timing of combustion inthe combustion chamber. When supporting the tool during operation, theoperator can grip the throttle with the handle [9 to maintain thethrottle fully open and at the same time apply the brake with his indexfinger to control the timing of combustion. Very little energy isnecessary to apply the brake and the tool may be readily stopped byincreasing the pressure by the index finger.

This application is a continuation in part of application Serial No.496,709 filed July 30, 1943 for Internal Combustion Percussion Tool, nowPatent Number 2,433,007.

I claim:

1. In an internal combustion percussion tool, the combination of acasing having a combustion chamber, a timing piston reciprocable in saidI combustion chamber to control the combustion of fuel therein, apercussion working piston reciprocable in the combustion chamber anddriven in a working direction by the combustion of fuel and returned byexhaust gas, a crankshaft cari ried by the casing and operated by thetiming piston, a throttle carried by the casing for regulating thesupply of fuel to the combustion chamber, and manually operated brakemeans positioned to be actuated simultaneously with the throttle forapplying a load on the crankshaft to control the speed of the timingpiston and regulate the frequency of reciprocation of the workingpiston.

2. In an internal combustion percussion tool, the combination of acasing having a combustion chamber, a timing piston reciprocable in saidcombustion chamber to control the combustion of fuel therein, apercussion working piston reciprocable in the combustion chamber anddriven in a working direction by the combustion of fuel and returned byexhaust gas, a crankshaft carried by the casing and operated by thetiming piston, a brake pulley secured to said crankshaft, a brake bandarranged to be contracted on said pulley, and a finger engaging surfaceattached to said brake band for applying a load on the crankshaft tocontrol the speed of the timing piston independently of the combustionof fuel and regulate the frequency of reciprocation of the workingpiston.

3. In an internal combustion percussion tool, the combination of acasing having a guide handle and a combustion chamber, a timing pistonreciprocable in said combustion chamber to supply and ignite the fueland control the exhaust of the products of combustion from thecombustion chamber, a percussion working piston reciprocable in thecombustion chamber and driven in a working direction by the combustionof fuel and returned by exhaust gas, a throttle pivoted on the guidehandle for regulating the flow of fuel supply, a crankshaft carried bythe casing and operated by the timing piston, brake means on saidcrankshaft, and a finger control carried by the guide handle andpositioned to be actuated simultaneously with the throttle for applyinga load through the brake on the crankshaft to control the speed of thetiming piston and regulate the frequency of reciprocation of the workingpiston without decreasing the power of combustion.

4. In a percussion tool, the combination of an internal combustionengine having a timing piston operating to control the combustion offuel therein and a percussion working piston driven in a workingdirection by the combustion of fuel and returned by the pressure ofexhaust gas, and manually operated brake means effective to control thespeed of the timing piston independently of its operation and the amountof fuel supplied to the combustion chamber to regulate the frequency ofoperation of the working piston.

CARL S. WEYANDT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,490,850 Porsche Apr. 15, 19241,920,765 Rasch Aug. 1, 1933 2,433,007 Weyandt Dec. 23, 1947

